With these arrangements there is no demagnetizing force to be considered, for the ring has not any ends to produce one, and the force due to the ends of a rod 400 or 500 diameters in length is quite insensible at the middle portion; H therefore is equal to Ho.
From data contained in Joule's paper it may be calculated that the strongest external field Ho produced by his coil was about 126 C.G.S.
On oxidation it yields ortho-carboxy-hydrocinnamic acid, HO 2 C C 6 H 4 CH 2 CH 2 C02H.
Pyrophosphoric acid, 'H' 4 P 2 0 7, is a tetrabasic acid which may be regarded as derived by eliminating a molecule of water between two molecules of ordinary phosphoric acid; its constitution may therefore be written (HO) 2 0P O PO(OH) 2.
A deep red solution was obtained, but the free quinone was not isolated since the solution on standing deposits nearly black crystals of dihydroxyphenylhydroxybenzoquinone (HO)2C6H3 C6H202.OH.